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Table fieldType change at runtime

Posted on 2003-03-11
Medium Priority
Last Modified: 2007-12-19
I have an access table, at RUNTIME in delphi I want to change the type of from numeric to Tekst or from tekst to numeric, is that possible?
Question by:Rody

Expert Comment

ID: 8117902
Why don't you try to store the value from this field into the desired type of data.

  MyNum : real;
  MyStr : string;
   MyNum := StrToFloat(MyDataSet.FieldByName(<YourField>).AsString);
   MyStr := FloatToStr(MyDataSet.FieldByName(<YourField>).AsFloat);

Hope this helps,
LVL 14

Expert Comment

ID: 8117927
check out IntToStr and StrToInt

Author Comment

ID: 8118609
People, I know that all, but I want to change the type of fiels in the database, because of the following problem:

I have mdb file and I am working with, after that I have to download the nieuw version of mdb from an ftp site, and I have to work with the nieuw mdb. the local old file that I have has an autonumeric field, and the table that I am downloading has that field as Numeric, do u understaand the problem???
Thats why I want to change that field type from Nummeric to auto nummeric...
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Expert Comment

ID: 8118897
I don't think that the field type can be changed at Runtime. Or better - I didn't see or try that yet.

But if you have some data in that database you could save them to some arrays, then create whole new DB with new field definitions and then save the data in arrays back.

However, you sholdn't be very satisfied with this solution if there will be some BLOB (or MEMO or something like that) data saved there.

Expert Comment

ID: 8123467
You must do the following:

1. Unload the table (possibly you can rename it)
2. Create the replacement table
3. Load the new table with the old data

Access does this internally if you try to do it in their designer, they just hide all of that from you.  

If you need a generic mechanism then I suggest a medeval torture device - to convince your data modeller that he should figure out the final format real fast.  :o)

As an alternative, say if your data modeller is much bigger and faster than you are, you can rename the old table, construct the new one, and then copy the data from one to the other using the query "insert into NewTable select * from OldTable".

Since access allows you to link across databases, the old table can simply be linked into the new database and the query will work just fine.

I wouldn't use arrays because arrays aren't large enough to satisfy the potential for a database.  

Accepted Solution

swift99 earned 105 total points
ID: 8123493
Since your real problem was numeric to autonumber, this should work okay.

For text to numeric and the converse, you would list the individual columns and cast the values in the query.

Author Comment

ID: 8134478
Thanks for the tip

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